Put a new motor in my 2000 s80 t6 and at first started up fine! A day later the idle acts funny. It takes a sec to start n it idles high then drops low and tries to go back to normal but continuously drops low until the car eventually dies! I tried looking for vacuum leaks and a diagram.. I've had no luck with either! It had threw out o2 codes, but didn't before the engine was changed. Dealer says it needs to be tuned, another shop says something with the throttle, and me somethings not plugged in right.. that's what I am left with! I need some help here!